Initial commit: Developer Tools MVP with visual editor

- Complete React app with 7 developer tools
- JSON Tool with visual structured editor
- Serialize Tool with visual structured editor
- URL, Base64, CSV/JSON, Beautifier, Diff tools
- Responsive navigation with dropdown menu
- Dark/light mode toggle
- Mobile-responsive design with sticky header
- All tools working with copy/paste functionality

node_modules/stop-iteration-iterator/index.js

@@ -0,0 +1,46 @@
+'use strict';
+
+var SLOT = require('internal-slot');
+var $SyntaxError = require('es-errors/syntax');
+
+var $StopIteration = typeof StopIteration === 'object' ? StopIteration : null;
+
+/** @type {import('.')} */
+module.exports = function getStopIterationIterator(origIterator) {
+	if (!$StopIteration) {
+		throw new $SyntaxError('this environment lacks StopIteration');
+	}
+
+	SLOT.set(origIterator, '[[Done]]', false);
+
+	/** @template T @typedef {T extends Iterator<infer U> ? U : never} IteratorType */
+	/** @typedef {IteratorType<ReturnType<typeof getStopIterationIterator>>} T */
+	var siIterator = {
+		next: /** @type {() => IteratorResult<T>} */ function next() {
+			// eslint-disable-next-line no-extra-parens
+			var iterator = /** @type {typeof origIterator} */ (SLOT.get(this, '[[Iterator]]'));
+			var done = !!SLOT.get(iterator, '[[Done]]');
+			try {
+				return {
+					done: done,
+					// eslint-disable-next-line no-extra-parens
+					value: done ? void undefined : /** @type {T} */ (iterator.next())
+				};
+			} catch (e) {
+				SLOT.set(iterator, '[[Done]]', true);
+				if (e !== $StopIteration) {
+					throw e;
+				}
+				return {
+					done: true,
+					value: void undefined
+				};
+			}
+		}
+	};
+
+	SLOT.set(siIterator, '[[Iterator]]', origIterator);
+
+	// @ts-expect-error TODO FIXME
+	return siIterator;
+};